0004956: Printf format: %v or %V to print any value

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0004956

OCaml

OCaml general

public

2010-01-07 11:41

2011-12-09 11:08

Reporter

Bardou

Assigned To

Priority

normal

Severity

feature

Reproducibility

N/A

Status

acknowledged

Resolution

open

Platform

OS Version

Product Version

3.11.1

Target Version

Fixed in Version

Summary

0004956: Printf format: %v or %V to print any value

Description

The idea is to be able to write :

Printf.printf
  "Hello %v, %v and %v are OCaml values"
  "user name"
  1
  [ true; false ];

Which would print something like :

Hello "user name", 1 and [ true; false ] are OCaml values

Additional Information

This would be very useful especially when debugging.

The toplevel already contains a mechanism to print any type, except functions and abstract values. The same printing conventions could be used. In particular : functions could be printed as <fun>, abstract values as <abstr>.

A mechanism should be added to the typing of formats so that %v (or %V) accepts any value type. Then, code generation could use the type information to produce the correct printer.

This correct printer cannot be produced for polymorphic values, but they could be printed as <poly>.

Maybe %V is better than %v, as the convention seems to be that uppercase letter use OCaml conventions.

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Notes
(0005227) weis (developer) 2010-01-12 10:01	This is a major feature wish that requires careful thinking and a lot of work! Furthermore, we would not have a completely satisfactory solution in the end (due to this <poly> catch all case that tend to propagate, as far as you use polymorphic functions). The correct solution to get this feature in its full glory is a major modification of the type system along the lines of G'Caml. In short, a natural feature wish in a strongly typed polymorphic language; we had it in mind for decades; unfortunately, we are not yet ready to offer it, even in the rather limited extent you proposed.

Issue History
Date Modified	Username	Field	Change
2010-01-07 11:41	Bardou	New Issue
2010-01-07 15:22	doligez	Status	new => acknowledged
2010-01-12 10:01	weis	Note Added: 0005227